1. Field of the Invention
The present invention relates to an illumination control device which can be used for illumination of a vehicle etc.
2. Description of the Related Art
For example, it is assume that a cabin is illuminated in a vehicle such as a passenger vehicle. In this case, it is desired that the cabin is illuminated by illumination light with proper chromaticity in accordance with the state at that time. In such an application, for example, a full-color LED device containing a plurality of light-emitting elements (LEDs: Light-Emitting Diodes) emitting lights at red (R), green (G) and blue (B) color wavelengths respectively is used as a light source. Thus, it is possible to obtain illumination light with various chromaticities if necessary.
On the other hand, a related-art technique for calibrating an illumination device is disclosed, for example, in JP-A-2007-59179. In the illumination device according to JP-A-2007-59179, illumination light is radiated to an illuminance/chromaticity calibration tool provided with an RGB color pattern, intensities of lights emitted from respective color LED groups are acquired in accordance with the respective R, G and B color components based on a result of imaging the color pattern by a CCD camera, and characteristics about illuminances and chromaticities of the respective color LED groups are calculated.
In addition, JP-T-2010-538434 (WO2009/034060) discloses a technique for adjusting the color, color temperature or chromaticity coordinates of mixed light radiated from an LED spot light so as to keep the color, color temperature or chromaticity coordinates of the mixed light constant. In addition, JP-A-2014-134527 discloses a technique for calibrating a variation (machine difference) in a measurement result caused by the type of an LED measurement device used for inspection of an LED.
For example, when a full-color LED device is used as a light source, the device itself has a very large individual difference in light emission characteristic. Therefore, when the full-color LED device is used as a light source of an illumination device for illuminating a cabin, there is a case in which illumination light with desired chromaticity estimated at design cannot be obtained.
In addition, an LED light source has a small light emission quantity in comparison with an ordinary lamp. Therefore, it is necessary to dispose a plurality of LED light sources at a plurality of places respectively in a cabin and light these light sources simultaneously in order to illuminate the cabin as a whole. However, since there is a large variation in light-emitting characteristic due to individual differences among the LED devices, hue of illumination perceived by a user may differ from one place to another in the cabin.
Accordingly, it is necessary to suppress the hue of the illumination from differing from one place to another, or to perform the illumination so as to obtain illumination light with desired chromaticity. Accordingly, special LED devices which have been selected beforehand must be used so that individual differences among the LED devices in actual use can be limited to be small. In addition, only the special LED devices selected in conformity with predetermined criterions are allowed to be used. Accordingly, component cost of each LED device to be used inevitably increases greatly in comparison with an ordinary LED device.